Network element discovery using a network routing protocol

ABSTRACT

A data processing apparatus comprises instructions to perform sending and receiving one or more messages conforming to a network routing protocol, such as Open Shortest Path First (OSPF); obtaining one or more information elements that specify one or more capabilities of the apparatus; creating a particular routing protocol message comprising an opaque advertisement that includes the one or more information elements; and sending the particular message on one of the network interfaces. For example, a router or switch that implements a network routing protocol can use OSPF Opaque Link State Advertisements to advertise and discover services and capabilities of other routers or switches.

FIELD OF THE INVENTION

The present invention generally relates to network management. Theinvention relates more specifically to techniques for discovering thecapabilities or services of network nodes and the services that networknodes provide.

BACKGROUND

The approaches described in this section could be pursued, but are notnecessarily approaches that have been previously conceived or pursued.Therefore, unless otherwise indicated herein, the approaches describedin this section are not prior art to the claims in this application andare not admitted to be prior art by inclusion in this section. Further,nothing in this patent document is admitted to be prior art by theapplicant(s).

Discovering network nodes representing the endpoints of a networkcommunication path is a basic issue in setting up a communicationchannel. In most cases, the endpoint is either known in advance, or someidentifier is known and then used to discover the other informationabout the endpoint. For example, DNS lookup can be used, if the name ofan available DNS server is previously configured in a device.Alternatively, Service Location Protocol (SLP), as defined in IETF RFC2165 and RFC2608 can be used to locate an address of the endpoint.

Past approaches have included various methods of service detection andendpoint detection, generally based on manual deployment or provisioningand available networking standards. For networking devices from CiscoSystems, Inc., San Jose, Calif., and certain compatible devices, theCisco Discovery Protocol (CDP) can be used to discovery Cisco devicesthat are on the same link as the discovering device—that is, one hopaway—and their characteristics. Typically, a network administratorconfigures an endpoint or client with information about an availableserver, or some form of server load balancing is deployed to achievetransparency with respect to the location of the server.

However, manual provisioning is a deployment challenge, since all thenodes typically have to be re-configured when a new server or serverpool is introduced to the network. In situations where servertransparency is not feasible—for example, because the additional nodecannot be hidden behind a load-balancing device—the manual provisioningapproach is a deployment nightmare.

Further, when the nodes are network devices such as switches or routers,discovering what services are available at the nodes, and thecapabilities of the nodes, is more challenging compared to locatingclients, servers or other endpoints. In this context, there is a needfor some method or mechanism providing automatic service and nodecapability discovery. It would be useful to have an approach in whichmanual provisioning is limited to a single new node that is deployed inthe network. There is a need for an approach that allows all other nodesto learn about the new node, and that allows the new node to learn aboutthe existing nodes in the network.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 is a block diagram that illustrates an overview of a networkarrangement in which an embodiment may be used;

FIG. 2 is a flow diagram that illustrates a high level overview of oneembodiment of a method for network element capability discovery using anetwork routing protocol, as performed by a discovering element;

FIG. 3 is a flow diagram that illustrates a high level overview of oneembodiment of a method for network element capability discovery using anetwork routing protocol, involving processing received discoveryinformation; and

FIG. 4 is a block diagram that illustrates a computer system upon whichan embodiment may be implemented.

DETAILED DESCRIPTION

Apparatus and methods for network element capability discovery using anetwork routing protocol are described. In the following description,for the purposes of explanation, numerous specific details are set forthin order to provide a thorough understanding of the present invention.It will be apparent, however, to one skilled in the art that the presentinvention may be practiced without these specific details. In otherinstances, well-known structures and devices are shown in block diagramform in order to avoid unnecessarily obscuring the present invention.

Embodiments are described herein according to the following outline:

1.0 General Overview

2.0 Structural and Functional Example

3.0 Implementation Mechanisms—Hardware Overview

4.0 Extensions and Alternatives

1.0 General Overview

The needs identified in the foregoing Background, and other needs andobjects that will become apparent for the following description, areachieved in the present invention, which comprises, in one aspect, adata processing apparatus, comprising one or more processors; one ormore network interfaces coupled to the processors and communicativelycoupled to a telecommunications network; a computer-readable mediumcomprising one or more sequences of one or more instructions which, whenexecuted by the one or more processors, cause the one or more processorsto perform sending and receiving one or more messages conforming to anetwork routing; obtaining one or more information elements that specifyone or more capabilities of the apparatus; creating a particular routingprotocol message comprising an opaque advertisement that includes theone or more information elements; and sending the particular message onone of the network interfaces.

In one feature of this aspect, the apparatus further comprises sequencesof instructions which, when executed by the processor, cause theprocessor to perform receiving, from a node that is coupled to thenetwork, a second particular message comprising a second opaqueadvertisement that includes one or more second information elements thatdescribe capabilities of the node; storing, in a data repository of theapparatus, an identification of the node in association with the one ormore second information elements; determining one or more services orcapabilities that the one or more second information elements describe;and creating and sending to the node, a request for the one or moreservices or capabilities.

In various embodiments, the network routing protocol comprises OpenShortest Path First (OSPF) protocol or Intermediate System/IntermediateSystem (IS/IS).

In various other features, the one or more information elements describea version of a software element that is hosted on the apparatus; a roleof a software element that is hosted on the apparatus; a policy that isused by a software element that is hosted on the apparatus; a digitalcertificate for a software element that is hosted on the apparatus; anda processing load metric for the apparatus.

In other aspects, the invention encompasses a method and acomputer-readable medium configured to carry out the foregoing steps.

2.0 Structural and Functional Example

FIG. 1 is a block diagram that illustrates an overview of a networkarrangement in which an embodiment may be used. A network element 102Ais coupled to a telecommunications network 120 that includes a secondnetwork element 130, which is further coupled to another network element102B. Network elements 102A, 130, 102B are routers, switches, or otherelements of infrastructure of a packet-switched network.

In an example embodiment, network element 102A comprises an operatingsystem 104A, routing protocol agent 106A, routing protocol discoverylogic 108A, and application 110A. Operating system 104A supervises othersoftware elements and controls the use of hardware resources. In oneembodiment, operating system 104A is Cisco IOS® Software from CiscoSystems, Inc., San Jose, Calif., ION, or IOX. Alternatively, operatingsystem 104A is LINUX or a BSD UNIX based operating system.

Routing protocol agent 106A comprises one or more software elements thatimplement a network routing protocol. Example routing protocols includeOSPF, IS/IS, etc. Preferably, a link state protocol that provides linkstate messages, packets or advertisements (LSPs, LSAs) is used. Routingprotocol agent 106A is shown in FIG. 1 as separate from operating system104A, but in an alternative embodiment, the operating system includesthe routing protocol agent. In a LINUX embodiment, routing protocolagent 106A can comprise the Quagga/Zebra implementation of OSPF, whichsupports Opaque LSAs as further described herein.

Routing protocol discovery logic 108A comprises one or more softwareelements that implement the functions and processes that are describedfurther herein in connection with FIG. 2, FIG. 3. Generally, routingprotocol discovery logic 108A functions to determine, using routingprotocol messages or packets, capabilities and services of networkelement 102B or other network elements in network 120. Routing protocoldiscovery logic 108A is shown in FIG. 1 as separate from operatingsystem 104A, but in an alternative embodiment, the operating systemincludes the routing protocol discovery logic.

Application 110A represents any other functional element of networkelement 102A that can benefit from determining services or capabilitiesof another network element. For example, application 110A may comprisean agent, service, blade, or process that might change its behaviordepending on the services or capabilities of other network elements. Asone specific example, application 110A is an application-orientednetworking services (AONS) blade. AONS routers are available from CiscoSystems, Inc.

Network element 102B has an internal structure similar to networkelement 102A and comprises an operating system 104B, routing protocolagent 106B, routing protocol discovery logic 108B, and application 110Bhaving the characteristics given above for operating system 104A,routing protocol agent 106A, routing protocol discovery logic 108A, andapplication 110A. Network element 130 is a conventional router or switchthat does not include the foregoing elements. Alternatively, networkelement 130 has the same structure as network elements 102A, 102B.

For purposes of illustrating a clear example, FIG. 1 shows three networkelements 102A, 102B, 130. However, other practical embodiments mayinclude any number of network elements distributed across one or morenetworks or internetworks. Network 120 may be a LAN, WAN, internetwork,or combination thereof. As further described below, network elements102A, 102B, 130 send and receive capability discovery message data usinga routing protocol as a transport mechanism. The network elements 102A,102B, 130 can “peer” with other routing elements, such as routers andswitches, to exchange routing information using the routing protocol.

FIG. 2 is a flow diagram that illustrates a high level overview of oneembodiment of a method for network element capability discovery using anetwork routing protocol, as performed by a discovering element. FIG. 3is a flow diagram that illustrates a high level overview of oneembodiment of a method for network element capability discovery using anetwork routing protocol, involving processing received discoveryinformation. For purposes of illustrating a clear example, FIG. 2 isdescribed first with reference to steps that network element 102Aperforms to advertise its capabilities or services to network element102B or other network elements.

At step 202, messages that conform to a network routing protocol aresent and received. For example, network element 102A sends and receivesOSPF packets. Step 202 broadly represents initiation and use of anetwork routing protocol, such as OSPF, at a first network element. Theparticular content of the messages or packets is unimportant.

At step 204, one or more information elements are obtained that specifyone or more capabilities or services. For example, routing protocoldiscovery logic 108A retrieves information from a configuration file,SNMP MIB, or application 110A that describes the attributes,capabilities or services of network element 102A. The particularmechanism that is used to obtain the information elements is notcritical, provided that some mechanism is used to create or determine aset of information that describes one or more attributes, capabilitiesor services of the network element.

Example information that can be advertised in the information elementsincludes, but is not limited to, the network address of a networkelement; version identifying information for an application, operatingsystem, agent or other logic that is hosted on the network element; arole of the network element or an application, agent or other logic thatis hosted on the network element; policies that are configured on anode; a digital certificate of the node; software adapters that areavailable on a node; compression algorithms that are available on anode; and other information.

Other example information includes state values or attributes indicatingstate characteristics of a node. For example, information elements cancomprise metrics indicating current processing load or capability of thenode, to help a receiving node determine whether to route requests tothe sending node; and other information about capabilities or services.Other state information of a node can be dynamically conveyed; forexample, an increase or decrease in CPU load by a certain factor cantrigger routing protocol discovery logic to initiate a new opaqueadvertisement that identifies the new CPU load value.

At step 206, a message is created in the network routing protocol thatincludes an opaque field that carries the information elements. Forexample, routing protocol discovery logic 108A creates an OSPF packetcomprising an OSPF Opaque Link State Advertisement (opaque LSA) and theinformation elements are placed in a field of the opaque LSA designed inOSPF to carry opaque data. “Opaque,” in this context, means not modifiedby a router or other device that implements the routing protocol andreceives and forwards the message or packet. OSPF Opaque LSAs aredefined in IETF RFC 2370. The information elements can be packaged in anOSPF Opaque LSA using a vendor-specific extension to the LSA, whichdefines the structure or format for the opaque data. The particular useof OSPF described herein is not contemplated in RFC 2370.

At step 208, the message is sent using the network routing protocol. Forexample, routing protocol discovery logic 108A hands off, to routingprotocol agent 106A, the OSPF packet created in step 206, and therouting protocol sends the packet on an interface of network element102A.

When the routing protocol is OSPF, sending the packet automaticallycauses all routers in network 120 with OSPF agents to forward the packetto all other routers to which they have connectivity. Because the OSPFpacket is an Opaque LSA, routers that do not support the approach herein(for example, network element 130 of network 120 in FIG. 1) do notmodify the contents of the packet, but always forward the OSPF packetsto peers. Therefore, the information elements describing attributes,capabilities and services of network element 102A are propagatedthroughout the network rapidly and without modification. Further, areceiving network element that implements the approaches herein, such asnetwork element 102B, can extract the information about attributes,capabilities or services and use that information, as now described.

Since any change in the opaque information that is propagated causes achange in the opaque LSA, in an OSPF implementation LSA flooding mayoccur. To reduce the likelihood of flooding in the network, routingprotocol discovery logic 108A can accumulate changes in capabilities orservices over a specified period of time, and send an OSPF Opaque LSA toadvertise an updated set of attributes, capabilities or services only atspecified intervals. For example, attributes, capabilities or servicesof a node or router can be advertised using the approach herein onlyonce per day or once per 12 hours. Alternatively, only significantchanges in attributes, capabilities or services can be advertised.Further, the opaque information can be broken down into fragments toreduce flooding overhead.

Referring now to FIG. 3, step 302 comprises receiving, from a networknode, a particular message that conforms to a network routing protocoland includes one or more information elements that specify one or morecapabilities or services. For example, network element 102B receives theOSPF packet that network element 102A sent at step 208 of FIG. 2.

In step 304, an identification of the node that sent the message, inassociation with the information elements that specify one or moreattributes, capabilities or services, are stored in a data repository.For example, network element 102B stores, in an SNMP MIB, database, orother data repository, information identifying network element 102A andthe contents of the OSPF Opaque LSA that was received. Identifyinginformation can comprise a router name, source IP address, label value,etc.

Step 304 can involve storing the Opaque LSA as an atomic object in therepository, or parsing the Opaque LSA to identify particular informationelements. For example, network elements 102A, 102B can host the sameversion of routing protocol discovery logic 108A, 108B, which canimplement a particular format for the information in an Opaque LSA thatadvertises attributes, capabilities or services. The format can specifyan order of name, value pairs, or a header followed by a capabilitieslist, etc. The particular schema used to organize data within the OpaqueLSA is not critical, and if both network elements 102A, 102B support thesame logic, then a receiving network element can parse and determinewhat capabilities or services are represented in the Opaque LSA.

At step 306, the receiving network element determines one or moreattributes, services or capabilities that the information elementsdescribe. Step 306 can involve parsing data that was stored in therepository, or correlating parsed data in the repository to other datato result in an identification of a particular attribute, capability orservice. Step 306 also can comprise passing the information elements toapplication 110B, which can then parse or interpret the informationelements to determine attributes, capabilities or services of networkelement 102A. Thus, step 306 broadly represents any action taken withinnetwork element 102B to determine what attributes, capabilities orservices are represented in the received information elements and howthey can be used.

In step 308, a request for one or more of the services or capabilitiesis sent. For example, in step 306 network element 102B determines thatthe other network element 102A hosts an enterprise user-role database,and that application 110B needs to determine an enterprise role for auser named “john_doe”; therefore, network element 102B forms and sendsnetwork element 102A a request to resolve the user name into a role.Thus, step 308 broadly represents any invocation by network element 102Bof attributes, capabilities or services of network element 102A.

Further, FIG. 3 broadly represents the concept that a receiving networkelement implementing the approaches herein can discover, storeinformation describing, and invoke the attributes, capabilities orservices of another node in the network, by interpreting informationcarried in a payload of an opaque routing protocol message or packetthat the other node advertises or floods using the routing protocol.

Accordingly, in an embodiment, a data processing apparatus comprisesinstructions to perform sending and receiving one or more messagesconforming to Open Shortest Path First (OSPF) protocol; obtaining one ormore information elements that specify one or more capabilities of theapparatus; creating a particular OSPF message comprising an OSPF OpaqueLink State Advertisement that includes the one or more informationelements; and sending the particular OSPF message on one of the networkinterfaces. For example, a router or switch that implements a networkrouting protocol can use opaque information elements in routing protocolpackets to discover services and capabilities of other routers orswitches.

For purposes of illustrating a clear example, certain parts of thedescription herein refer to OSPF Opaque LSAs. However, in otherembodiments, other network layer routing protocols are adapted to enablea network infrastructure element, such as a router or switch, todiscover services and capabilities of other network elements. Forexample, IS/IS can be used with new TLV definitions that carry serviceinformation. Further, EIGRP could be used with a new payload definitionto carry service information. BGP extended communities may be used tocarry service information in opaque payloads.

The approach herein provides numerous improvements over priorapproaches. For example, using OSPF for service discovery results infast discovery, because OSPF messages are processed rapidly withinrouters and propagate rapidly across networks. OSPF is widelyimplemented in nearly all routers and switches today, including AONSrouters from Cisco Systems. Further, OSPF implements several securitymechanisms, such as authentication and encryption on a per-link basisusing IPSec hop-by-hop tunnels, and physical security to limit access toinfrastructure devices. Typically MD5 message digest authentication isused, based on shared keys. The approach herein can leverage theseexisting mechanisms. Thus, communication of capabilities and services asprovided herein occurs securely by using such mechanisms.

The approach herein also interoperates with existing network elementsand imposes only a modest requirement upon network elements, such asnetwork element 130 of FIG. 1, that do not support the particularapproach herein; such elements are only required to support a routingprotocol and to pass an opaque routing protocol message. In a networkthat uses Cisco routers as the network elements, Cisco IOS® Softwarealready supports OSPF Opaque LSAs, and is capable of reliablytransporting any OSPF opaque payload.

A further benefit of the approach herein is that existing nodes in thenetwork do not require manual reconfiguration with information aboutservices or capabilities of a new or additional node that is deployed inthe network. If the new node is configured with information about itscapabilities or services, the new node can advertise the capabilitiesand services using the approach herein and all other existing nodes inthe network will automatically acquire corresponding capability andservice information.

Further, no new protocol or additional protocol is needed to implementservice discovery; an existing routing protocol can be used in anembodiment.

Implementations that use OSPF can benefit from the short convergencetime of OSPF. For example, because OSPF link state advertisementmechanisms allow a large number of widely distributed routers to rapidlyconverge on a common set of reachability information, with the approachherein an outage of service provided by a particular network element orthe loss of a particular capability at a particular network element isdetected quickly. As a result, other nodes can direct further traffic todifferent nodes in network that provide a required capability or adesired service. Thus, the approach herein can provide a “self healing”network in which available services or capabilities of network elements102A, 102B are known rapidly.

When a network element uses the approach herein to advertise that thenetwork element is an AONS node, then using OSPF link state databaseinformation, reachability to other AON nodes can be determineddynamically. Examples of reachability information include number ofhops, link load, etc.

4.0 Implementation Mechanisms—Hardware Overview

FIG. 4 is a block diagram that illustrates a computer system 400 uponwhich an embodiment of the invention may be implemented. The preferredembodiment is implemented using one or more computer programs running ona network element such as a router device. Thus, in this embodiment, thecomputer system 400 is a router.

Computer system 400 includes a bus 402 or other communication mechanismfor communicating information, and a processor 404 coupled with bus 402for processing information. Computer system 400 also includes a mainmemory 406, such as a random access memory (RAM), flash memory, or otherdynamic storage device, coupled to bus 402 for storing information andinstructions to be executed by processor 404. Main memory 406 also maybe used for storing temporary variables or other intermediateinformation during execution of instructions to be executed by processor404. Computer system 400 further includes a read only memory (ROM) 408or other static storage device coupled to bus 402 for storing staticinformation and instructions for processor 404. A storage device 410,such as a magnetic disk, flash memory or optical disk, is provided andcoupled to bus 402 for storing information and instructions.

A communication interface 418 may be coupled to bus 402 forcommunicating information and command selections to processor 404.Interface 418 is a conventional serial interface such as an RS-232 orRS-422 interface. An external terminal 412 or other computer systemconnects to the computer system 400 and provides commands to it usingthe interface 414. Firmware or software running in the computer system400 provides a terminal interface or character-based command interfaceso that external commands can be given to the computer system.

A switching system 416 is coupled to bus 402 and has an input interface414 and an output interface 419 to one or more external networkelements. The external network elements may include a local network 422coupled to one or more hosts 424, or a global network such as Internet428 having one or more servers 430. The switching system 416 switchesinformation traffic arriving on input interface 414 to output interface419 according to pre-determined protocols and conventions that are wellknown. For example, switching system 416, in cooperation with processor404, can determine a destination of a packet of data arriving on inputinterface 414 and send it to the correct destination using outputinterface 419. The destinations may include host 424, server 430, otherend stations, or other routing and switching devices in local network422 or Internet 428.

The invention is related to the use of computer system 400 for networkelement capability discovery using a network routing protocol. Accordingto one embodiment of the invention, network element capability discoveryusing a network routing protocol is provided by computer system 400 inresponse to processor 404 executing one or more sequences of one or moreinstructions contained in main memory 406. Such instructions may be readinto main memory 406 from another computer-readable medium, such asstorage device 410. Execution of the sequences of instructions containedin main memory 406 causes processor 404 to perform the process stepsdescribed herein. One or more processors in a multi-processingarrangement may also be employed to execute the sequences ofinstructions contained in main memory 406. In alternative embodiments,hard-wired circuitry may be used in place of or in combination withsoftware instructions to implement the invention. Thus, embodiments ofthe invention are not limited to any specific combination of hardwarecircuitry and software.

The term “computer-readable medium” as used herein refers to any mediumthat participates in providing instructions to processor 404 forexecution. Such a medium may take many forms, including but not limitedto, non-volatile media, volatile media, and transmission media.Non-volatile media includes, for example, optical or magnetic disks,such as storage device 410. Volatile media includes dynamic memory, suchas main memory 406. Transmission media includes coaxial cables, copperwire and fiber optics, including the wires that comprise bus 402.Transmission media can also take the form of acoustic or light waves,such as those generated during radio wave and infrared datacommunications.

Common forms of computer-readable media include, for example, a floppydisk, a flexible disk, hard disk, magnetic tape, or any other magneticmedium, a CD-ROM, any other optical medium, punch cards, paper tape, anyother physical medium with patterns of holes, a RAM, a PROM, and EPROM,a FLASH-EPROM, any other memory chip or cartridge, a carrier wave asdescribed hereinafter, or any other medium from which a computer canread.

Various forms of computer readable media may be involved in carrying oneor more sequences of one or more instructions to processor 404 forexecution. For example, the instructions may initially be carried on amagnetic disk of a remote computer. The remote computer can load theinstructions into its dynamic memory and send the instructions over atelephone line using a modem. A modem local to computer system 400 canreceive the data on the telephone line and use an infrared transmitterto convert the data to an infrared signal. An infrared detector coupledto bus 402 can receive the data carried in the infrared signal and placethe data on bus 402. Bus 402 carries the data to main memory 406, fromwhich processor 404 retrieves and executes the instructions. Theinstructions received by main memory 406 may optionally be stored onstorage device 410 either before or after execution by processor 404.

Communication interface 418 also provides a two-way data communicationcoupling to a network link 420 that is connected to a local network 422.For example, communication interface 418 may be an integrated servicesdigital network (ISDN) card or a modem to provide a data communicationconnection to a corresponding type of telephone line. As anotherexample, communication interface 418 may be a local area network (LAN)card to provide a data communication connection to a compatible LAN.Wireless links may also be implemented. In any such implementation,communication interface 418 sends and receives electrical,electromagnetic or optical signals that carry digital data streamsrepresenting various types of information.

Network link 420 typically provides data communication through one ormore networks to other data devices. For example, network link 420 mayprovide a connection through local network 422 to a host computer 424 orto data equipment operated by an Internet Service Provider (ISP) 426.ISP 426 in turn provides data communication services through the worldwide packet data communication network now commonly referred to as the“Internet” 428. Local network 422 and Internet 428 both use electrical,electromagnetic or optical signals that carry digital data streams. Thesignals through the various networks and the signals on network link 420and through communication interface 418, which carry the digital data toand from computer system 400, are exemplary forms of carrier wavestransporting the information.

Computer system 400 can send messages and receive data, includingprogram code, through the network(s), network link 420 and communicationinterface 418. In the Internet example, a server 430 might transmit arequested code for an application program through Internet 428, ISP 426,local network 422 and communication interface 418. In accordance withthe invention, one such downloaded application provides for networkelement capability discovery using a network routing protocol asdescribed herein.

The received code may be executed by processor 404 as it is received,and/or stored in storage device 410, or other non-volatile storage forlater execution. In this manner, computer system 400 may obtainapplication code in the form of a carrier wave.

5.0 Extensions and Alternatives

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense.

1. An apparatus, comprising: one or more processors; one or more networkinterfaces coupled to the processors and communicatively coupled to atelecommunications network; a computer-readable medium comprising one ormore sequences of one or more instructions which, when executed by theone or more processors, cause the one or more processors to perform:sending and receiving one or more messages conforming to a networkrouting protocol; obtaining one or more information elements thatspecify one or more capabilities or services of the apparatus; creatinga particular message that conforms to the network routing protocol andcomprises an opaque advertisement that includes the one or moreinformation elements; and sending the particular message on one of thenetwork interfaces.
 2. The apparatus of claim 1, further comprisingsequences of instructions which, when executed by the processor, causethe processor to perform: receiving, from a node that is coupled to thenetwork, a second particular message comprising a second opaqueadvertisement that includes one or more second information elements thatdescribe capabilities of the node; storing, in a data repository of theapparatus, an identification of the node in association with the one ormore second information elements; determining one or more services orcapabilities that the one or more second information elements describe;and creating and sending to the node, a request for the one or moreservices or capabilities.
 3. The apparatus of claim 1, wherein the oneor more information elements describe a version of a software elementthat is hosted on the apparatus.
 4. The apparatus of claim 1, whereinthe one or more information elements describe a role of a softwareelement that is hosted on the apparatus.
 5. The apparatus of claim 1,wherein the one or more information elements describe a policy that isused by a software element that is hosted on the apparatus.
 6. Theapparatus of claim 1, wherein the one or more information elementscomprise a digital certificate for a software element that is hosted onthe apparatus.
 7. The apparatus of claim 1, wherein the one or moreinformation elements describe a processing load metric for theapparatus.
 8. The apparatus of claim 1, wherein the network routingprotocol is any of Open Shortest Path First (OSPF) and IntermediateSystem/Intermediate System (IS/IS).
 9. An apparatus, comprising: meansfor sending and receiving one or more messages conforming to a networkrouting protocol; means for obtaining one or more information elementsthat specify one or more capabilities or services of the apparatus;means for creating a particular message that conforms to the networkrouting protocol and comprises an opaque advertisement that includes theone or more information elements; and means for creating and sending tothe node, a request for the one or more services or capabilities. 10.The apparatus of claim 9, further comprising: means for receiving, froma node that is coupled to the network, a second particular messagecomprising a second opaque advertisement that includes one or moresecond information elements that describe capabilities of the node;means for storing, in a data repository of the apparatus, anidentification of the node in association with the one or more secondinformation elements; means for determining one or more services orcapabilities that the one or more second information elements describe;and means for creating and sending to the node, a request for the one ormore services or capabilities.
 11. The apparatus of claim 9, wherein theone or more information elements describe a version of a softwareelement that is hosted on the apparatus.
 12. The apparatus of claim 9,wherein the one or more information elements describe a role of asoftware element that is hosted on the apparatus.
 13. The apparatus ofclaim 9, wherein the one or more information elements describe a policythat is used by a software element that is hosted on the apparatus. 14.The apparatus of claim 9, wherein the one or more information elementscomprise a digital certificate for a software element that is hosted onthe apparatus.
 15. The apparatus of claim 9, wherein the one or moreinformation elements describe a processing load metric for theapparatus.
 16. A machine-implemented method comprising: sending andreceiving one or more messages conforming to a network routing protocol;obtaining one or more information elements that specify one or morecapabilities or services of the apparatus; creating a particular messagethat conforms to the network routing protocol and comprises an opaqueadvertisement that includes the one or more information elements; andsending the particular message on one of the network interfaces.
 17. Themethod of claim 16, further comprising: receiving, from a second dataprocessing node that is coupled to the network, a second particularmessage comprising a second opaque advertisement that includes one ormore second information elements that describe capabilities of thesecond node; storing, in a data repository of the first node, anidentification of the second node in association with the one or moresecond information elements; determining one or more services orcapabilities that the one or more second information elements describe;and creating and sending to the second node, a request for the one ormore services or capabilities.
 18. The method of claim 16, wherein theone or more information elements describe a version of a softwareelement that is hosted on the first node.
 19. The method of claim 16,wherein the one or more information elements describe a role of asoftware element that is hosted on the first node.
 20. The method ofclaim 16, wherein the one or more information elements describe a policythat is used by a software element that is hosted on the first node. 21.The method of claim 16, wherein the one or more information elementscomprise a digital certificate for a software element that is hosted onthe first node.
 22. The method of claim 16, wherein the network routingprotocol is any of Open Shortest Path First (OSPF) and IntermediateSystem/Intermediate System (IS/IS).
 23. A computer-readable mediumcarrying one or more sequences of instructions, which instructions, whenexecuted by one or more processors, cause the one or more processors tocarry out the steps of: sending and receiving one or more messagesconforming to a network routing protocol; obtaining one or moreinformation elements that specify one or more capabilities or servicesof the apparatus; creating a particular message that conforms to thenetwork routing protocol and comprises an opaque advertisement thatincludes the one or more information elements; and sending theparticular message on one of the network interfaces.
 24. Thecomputer-readable medium of claim 23, further comprising sequences ofinstructions which, when performed by the one or more processors, causethe one or more processors to perform: receiving, from a second dataprocessing node that is coupled to the network, a second particularmessage comprising a second opaque advertisement that includes one ormore second information elements that describe capabilities of thesecond node; storing, in a data repository of the first node, anidentification of the second node in association with the one or moresecond information elements; determining one or more services orcapabilities that the one or more second information elements describe;and creating and sending to the second node, a request for the one ormore services or capabilities.